A supporting fabric of the type indicated above is known from, for instance, the article "Kunststofweefsels in practijk" by Ir. J. H. van Leeuwen in "Land+Water", No. 7/8, 1975 and from U.S. patent application serial No. 824,083, filed May 13, 1969, now abandoned. These known fabrics are often successfully used in building a road, dam or dike embankment on a subsoil having a low bearing capacity. On such bad subsoil, there is laid a supporting fabric on which subsequently a structure of sand, stones, clinker or other bulk material is formed. The bulk material structure of embankment may vary widely according to the locality and the structure to be made, for example, simple road surfacing, a motorway, a dike or a breakwater in the sea. For instance, the height of the layer of bulk material may range from about twenty cm to 10-20 m. The use of a supporting fabric on a subsoil leads to permanent stability of the raised structure and a proper, permanent separation between the subsoil and the raised structure. Furthermore, the load distribution effect of the supporting fabric consists in a reduction of point-to-point differences in consolidation, so that a re-distribution of stresses is obtained. The use of the known supporting fabric as a soil stabilizing means consequently leads to considerable savings, compared with the conventional method of working without the use of this type of soil stabilizing means. It may be generally stated that the supporting fabric has a stabilizing function, with the fabric being subjected mainly to a tensile load. The warp filaments in the known supporting fabric therefore have a high tensile strength and a limited elongation at break. The known supporting fabric has the disadvantage, however, that in addition to the elongation of the warp yarns, there occurs a fabric elongation which is due to crimp or contraction of the warp yarns. This fabric elongation particularly constitutes a problem as higher demands are made on the load to be taken up by the supporting fabric, particularly because in the case of the supporting fabrics previously used, the fabric elongation in proportion to the elongation of the warp yarns increases as heavier and stronger fabrics are employed. Another disadvantage to the known supporting fabric is that, upon being loaded, it is subject to transverse contraction, as a result of which its width is considerably reduced.
Netherlands Patent Application No. 64 05 171 describes a method of protecting dike structures in such a way that the embankment is reinforced by building in or covering with a netting of some synthetic material. The netting material to be used for it is obtained by weaving, knotting or using the Raschel method. This Netherlands Patent Application does not disclose or suggest the use of a supporting fabric comprising a straight warp, a binder warp and a weft.
According to German Offenlegungsschrift 2,000,937, the warp yarns of a reinforcing fabric are wrapped with threads to prevent the meshes from becoming smaller. The woven fabrics described in said patent application are destined for reinforcing bituminous sheet material. To achieve this end, the fabric must be particularly wide-meshed to permit the passage of the bituminous material through the meshes.
French Patent Specification No. 2,388,090 describes a knitted soil consolidation fabric, which has a lower bearing capacity than a woven fabric. Moreover, in the case of a knitted fabric, a less flexible construction is obtained, for in the manufacture of a knitted fabric with a straight warp and a binder wrap, the required amount of binder warp yarn is three times as high as that in the case of a woven fabric.
In British Patent No. 1,447,742, a method is described of reinforcing a foundation with the aid of a network comprising a system consisting of parallel threads of synthetic or glass fiber material and a system of parallel bands crossing and being connected to said system of threads. The parallel threads have a greater strength than the fibers of the system of bands. The stronger threads being regarded as warp threads, the binder warp threads of the present invention are not provided, which results in the above-described disadvantages. Further, the fabric according to said publication has fairly large meshes, so that these known fabrics are less suitable for use in earth filling structures.
In French Patent No. 2,214,001, a fabric is described for reinforcing objects of rubber. A separate thread is wound around the warp threads in such a way that the meshes are kept sufficiently large for the rubber compounds on either side of the fabric to be in contact with each other.
In German Offenlegungsschrift No. 2,053,891, a method is described of reinforcing a dam of sand or stones by the incorporation into it of loose flexible threads of some synthetic material.
Dutch Patent No. 7,007,249 describes a road or dike embankment covered with an asphalt layer. In this asphalt layer, or just underneath it, there is placed some commonly used reinforcing fabric of synthetic fibers.